1. Field of the Invention
This invention is in the field of producing a magnetic recording medium containing iron, including, for example, a magnetic medium including a composite Tb-FeCo magnetic film or a magnetic film of Fe-Co amorphous alloy which may be used for example as an optomagnetic recording medium, e.g., an optomagnetic disk capable of recording and reproducing by optical irradiation. The invention is also applicable to various magnetic media such as the usual magnetic recording media capable of recording and reproducing with a magnetic head or the like by usual electromagnetic induction.
2. Description of the Prior Art
There has been previously proposed a composite amorphous alloy composed of rare earth metals such as Tb and Gd, etc., and transition metals such as Fe and Co and the like, as an optomagnetic disc capable of writing reading by a laser beam, e.g., a semiconductor laser beam and also capable of being reloadable.
Generally, the method of vacuum evaporation is used as a method for forming the magnetic film for this type of magnetic medium. Specifically, such a vacuum evaporation is adopted from a resistance heating method wherein an evaporation source is heated to be evaporated, an electron beam or ion beam impact method wherein an electron beam or ion beam is impacted against the evaporation source to carry out evaporation, and by a sputtering method.
It is also known that the saturated intensity of magnetization Ms of a magnetic material is increased wherein nitrogen atoms are coupled with Fe, as compared with the case where the magnetic material contains Fe only.
In the magnetic medium such as an optomagnetic recording medium, a minimum diameter (d) of its recording bit is given by the equation d .alpha. Ew/(Ms.Hc), wherein Ms is the saturated intensity of magnetization; Hc is the coercive force, and Ew is the magnetic wall energy. According to the equation, when the saturated intensity of magnetization Ms is increased, it is evident that the diameter (d) of an information bit may be reduced, and accordingly high density of the magnetic material may be attained. Therefore, it is desirable that the saturated intensity of magnetization Ms of the magnetic medium be rendered as large as possible.
On the other hand, it is known that the saturated intensity of magnetization Ms is increased in the case that nitrogen atoms are coupled with Fe as the magnetic material, as compared with the case where the magnetic material contains Fe alone. Accordingly, it is known that various magnetic media such as optomagnetic recording media can consist of a magnetic film containing Fe coupled with nitrogen atoms.